The focus of research in the three laboratories that constitute this Program Project is the molecular basis of regulatory flow in early embryonic development. The Program Project will utilize the highly developed sea urchin and ascidian model systems for this research. Major objective are to develop functional comprehension of cis-regulatory systems that control genes expressed spatially in the early embryo, using genes that operate at different levels of the gene regulatory network; to discern the overall architecture of this network; and to discern the molecular mechanisms by which maternal transcription factors are activated, and control is transformed from maternal to zygotic regulatory processes. The three Research Components are:(1) Davidson Component, "Gene Regulatory Mechanisms and the Control of Early Embryogenesis"; (2) Fraser Component, "In Vivo Imaging of Gene Regulatory Events in the Early Embryo"; (3) Levine Component "Gene Regulation in the Ascidian Ciona intestinalis." The major aims of the Davidson Component are cis-regulatory analysis of genes expressed differentially in the sea urchin embryo, and identification and characterization of the maternal and zygotic transcription factors which control this expression. The major focus of the Fraser Component is visualization of the state of cis-regulatory elements in vivo and spatial visualization by new imaging methods of modifications of maternal transcription factors, using experimental systems characterized in the Davidson Component. The major focus of the Levine Component will be cis-regulatory analysis of certain key regulatory genes expressed in ascidian embryos, which are also to be characterized in the sea urchin embryo in the Davidson Component, and interphyletic gene transfer experiments to be carried out collaboratively between the Davidson and Levine labs. A salient characteristic of the proposed research is the engagement of powerful new technologies, some entirely novel. All the Components. Will rely on two Research Core Facilities, viz the SUMS Facility at Caltech's Marine Laboratory, which will provide sea urchins, gametes and nuclear extracts from which transcription factors are purified; and the Microsequencing Facility, where partially purified transcription factors are sequenced at picomole levels. An Administrative Core will oversee management, budget, and interlaboratory communication, with respect to material, financial, and intellectual matters.